The “default system” of the brain has been described as a set of regions which are ‘activated’ during rest and ‘deactivated’ during cognitively effortful tasks. To investigate the reliability of task-related deactivations, we performed a meta-analysis across 12 fMRI studies. Our results replicate previous findings by implicating medial frontal and parietal brain regions as part of the “default system”.However, the cognitive correlates of these deactivations remain unclear. In light of the importance of social cognitive abilities for human beings and their (...) propensity to engage in such activities, we relate our results to findings from neuroimaging studies of social cognition. This demonstrates a remarkable overlap between the brain regions typically involved in social cognitive processes and the “default system”.We, henceforth, suggest that the physiological ‘baseline’ of the brain is intimately linked to a psychological ‘baseline’: human beings have a predisposition for social cognition as the default mode of cognizing which is implemented in the robust pattern of intrinsic brain activity known as the “default system”. (shrink)
Wynn's claims are, in principle, entirely reasonable; although, as always, the devil is in the details. With respect to Wynn's discussion of the cultural evolution of artifactual symmetry, we provide a few more arguments for the utility of mirror symmetry and extend the enquiry into the tacit and explicit processing of natural and artifactual symmetry.
We outline some ways in which motor neglect (the underutilization of a limb despite adequate strength) and hysterical paralysis (failure to move a limb despite no relevant structural damage or disease) may throw light on the pathophysiology of catatonia. We also comment on the manifold inadequacies of distinguishing too firmly between symptoms of “neurologic origin” and of “psychiatric origin.”.
Commonly, a switch between networks mediating memory encoding and those mediating retrieval is observed. This may not only be due to differential involvement of neural resources due to distinct cognitive processes but could also reflect the formation of new memory traces and their dynamic change during consolidation. We used resting state fMRI to measure functional connectivity (FC) changes during post-encoding rest, hypothesizing that during this phase, new functional connections between encoding- and retrieval-related regions are created. Interfering and reminding tasks served (...) as experimental modulators to corroborate that the observed FC differences indeed reflect changes specific to post-encoding rest. The right inferior occipital and fusiform gyri (active during encoding) showed increased FC with the left inferior frontal gyrus and the left middle temporal gyrus (MTG) during post-encoding rest. Importantly, the left MTG subsequently also mediated successful retrieval. This finding might reflect the formation of functional connections between encoding- and retrieval-related regions during undisturbed post-encoding rest. These connections were vulnerable to experimental modulation: Cognitive interference disrupted FC changes during post-encoding rest resulting in poorer memory performance. The presentation of reminders also inhibited FC increases but without affecting memory performance. Our results contribute to a better understanding of the mechanisms by which post-encoding rest bridges the gap between encoding- and retrieval-related networks. (shrink)